The present invention relates to reciprocating piston internal combustion engines and more particularly to a barrel type or axial piston engine wherein the cylinders are arranged around a central drive shaft with their axis parallel thereto. Extensive patents on barrel engines have been granted for well over a century, as illustrated in the patent to Coney U.S. Pat. No. 16,229. Despite their early beginnings, barrel engines have not had any significant commercial successes in either the stationary or transportation fields. In aviation, barrel engines have had appeal because they were compact and required less frontal area and thus less drag on an aircraft with radial engines of comparative cylinder displacement. The most inefficient type of aircraft engine from a frontal area standpoint would be the radial engine when compared with the various in-line designs.
Early in this century a variety of prototype barrel engines were constructed and tested including the Almen engine in 1920, the Swiss Statax engine in 1913; the British Redrup axial engine in 1929, the U.S. Alfaro engine in the 1930's, and a German double-barreled engine (2 T 7/4-II) in the 1940's, all of which were intended for aircraft use. Barrel engines are compact because their pistons reciprocated parallel to the crankshaft rather than perpendicular. A variety of mechanisms and cylinder patterns have been explored such as opposing pistons sharing a common cylinder, as taught in Royal (U.S. Pat. No. 1,808,380) or opposing pistons sharing a common wobble plate or cam system, such as Palmer (U.S. Pat. No. 4,493,188).
In barrel engines the conversion of reciprocating piston motion to rotary driveshaft motion has been accomplished by a variety of designs such as swash plate and slipper arrangements, as shown in the patent to Mitchell (U.S. Pat. No. Re. 15,756); cylindrical cam and roller followers, as shown in the E. S. Hall SAE paper dated Mar. 14, 1940, entitled More Power from a Smaller Engine, FIG. 11, and wobble plates driven by offset shafts as shown in Almen (U.S. Pat. No. 1,255,973). The wobbler mechanisms are in turn connected to the pistons either directly or through connecting rods having pivotal joints at both ends thereof with numerous examples set forth in the above-mentioned SAE Paper by Hall in FIGS. 12 through 33. In spite of the reduced envelope advantages offered by barrel engines, none of the above-mentioned barrel engines ever achieved commercial success over the conventional radial or in-line engines which are driven by conventional crankshafts as known today. The only area wherein axial piston devices have achieved commercial success has been in the field of hydraulic pumps and motors which is a substantially different environment and area of technology from internal combustion piston engines. The nature of the loads, temperatures, pressure gradients, vibratory inputs from combustion and elasticity of the mechanism are all different.
In the patent to Cook et al (U.S. Pat. No. 3,018,737), a hydraulic pump is shown wherein the offset portion of the driveshaft drives the wobble plate and is mounted in a cantilevered fashion to the stationary cylinder block of the pump.
The patents to Akao (U.S. Pat. No. 4,872,431) and Clementz (U.S. Pat. No. 1,480,506) illustrate overhead cam and valve geometries somewhat similar to applicant's designs.